engineering quiz

S

sweatybetty

New member










A Backhoe weighing 8 tons is on top of a flatbed trailer and heading east on Interstate 70 near Hays, Kansas. The extended shovel arm is made of hardened refined steel and the approaching overpass is made of commercial-grade concrete, reinforced with 1 1/2 inch steel rebar spaced at 6 inch intervals in a crisscross pattern layered at 1 foot vertical spacing.

Solve: When the shovel arm hits the overpass, how fast do you have to be going to slice the bridge in half? (Assume no effect for headwind and no braking by the driver...)





Extra Credit: Solve for the time and distance required for the entire rig to come to a complete stop after hitting the overpass at the speed calculated above.

















ANSWER IS BELOW

[image]
bridge1.jpg
[/image]

[image]
bridge2.jpg
[/image]

[image]
bridge3.jpg
[/image]


Answer - Who cares, the trucking company just bought themselves a bridge.
/ubbthreads/images/graemlins/smiliesmack.gif
 
A good example of physics in action! /ubbthreads/images/graemlins/blush.gif Ouch!!!!!!!! Would have hated to have been crossing that bridge right then... /ubbthreads/images/graemlins/shocked.gif /ubbthreads/images/graemlins/confused.gif
 
Quote:
Would have hated to have been crossing that bridge right then.



That was my first thought, too!
 
At least when something like that happens you know immediately something has gone awry, and secondly the best part of your day is over, it's downhill from now on. /ubbthreads/images/graemlins/smiliesmack.gif /ubbthreads/images/graemlins/smiliesmack.gif
 
Wow, thats pretty amazing. Yeah, that would be a bummer to be driving across that overpass and have something like that jump up in front of you.
 
Man he had to be moving pretty good to make it that far!
It's amazing it cut in that far. Must have nailed it in the weekest part of the bridge.

We had a Case 621C Wheel Loader hit a low bridge in San Antonio once and all it did bend the cab back to a 30 degree angle and blow out all the glass.
We continued to use it for a couple of weeks before the new cab arrived...Another wheel loader that could lift 15,000 lbs couldn't even begin to straighten it out.
 
Quote:
How much do you think that cost? I am thinking in the between 2 and 5 million! That would wake you up if you were driving the truck?


Certainly no less and possibly much more.

Jack
 
OK, one of you engineering wizards help me out with this one for a minute.

Here is what I don't understand. If the boom is sticking out of the bridge, lets say a modest 12ft?? Like in the below picture:

bridge3.jpg


Then how in the heck did he not damage the side of the bridge what so ever? Like in the area I pointed out in this picture?

bridge1.jpg


Anyone?

Assuming the rig was traveling right to left, because it shows the tail end of the semi trailer, if the boom struck the bridge it would cause the bucket to raise up which does justify the damage over the cab, but theres no way the boom could end up in the position that it's in right now in the pics without taking out the side of the bridge, but yet in all the pics the bridge railing are perfect..

Is it possible that the cab end came down so hard after the initial impact that it forced the boom up through the bridge? If so then he was going really, really fast.
 

I was a conductor riding on freight trains for many years and let me tell you that weight like that unit going even at slow speeds can do unbelievable things! We hit a semi loaded with grain one day... lifted it intact and rolled it completetly up and over the top of the locomotives! That was a real rush seeing and hearing that thing scraping the roof of our cab! We were only going 12miles an hour!!!!! /ubbthreads/images/graemlins/shocked.gif
 
When the boom hit the bridge, it damaged the concrete face, and bounced towards the ground, unhooking the trailer. Then the boom came upward again and pierced the bridge.
Any other questions. /ubbthreads/images/graemlins/grin.gif
 
the part of the boom that you see sticking up through the overpass was pointing forward in front of the cab of the ho. it struck the overpass with the point that is highest in the picture. at the speed the truck was traveling it had enough force when it struck the overpass to go through the deck of the overpass. and force it back making it pivot and go strait up. the cab then came up and hit the under side of the overpass . then landed half on half off the trailer .
icebox
 
OH NO HE DIDN'T!

guess that low-boy trailer wasn't quite low enough...

I've seen plenty of "sardine can" trailer jobs on low bridges, but that one takes the cake!
 


Write your reply...
Back
Top